Detailed explanation of substation automation system

1, features <br> <br> complete substation automation system in addition to the means to retain the emergency manual operation means in the jump control and protection, closing, and all the rest of control, monitoring, measurement and alarm function can be monitored by a computer system carry out. The substation does not need to have a separate remote control device. The monitoring system fully satisfies the functions of remote signaling, telemetry, remote control, and remote adjustment, as well as the need for unattended operation. From the perspective of system design, it has the following features:

(1) Distributed Design. The system adopts a modular, distributed and open structure. Each control and protection function is distributed in the switch cabinet or control protection unit on the control cabinet as close as possible to the switch. All signals of control, protection, measurement, and alarm are processed in the local unit. After the data signal is transmitted to the monitoring computer of the main control room via the optical fiber bus, each local unit is independent and does not influence each other.

(2) Centralized design. The system adopts a modular and centralized cabinet structure. Each control and protection function is centralized in a dedicated collection and control cabinet. All signals of control, protection, measurement, and alarm are collected and controlled in the protection cabinet and processed into data signals. The fiber optic bus is transmitted to the monitoring computer in the main control room.

(3) Simple and reliable. Thanks to the replacement of conventional relays with multifunction relays, secondary wiring can be greatly simplified. The distributed design connects between the switchgear and the main control room; the centralized design is limited to the connection between the switchgear and the main control room. Its characteristic is that the wiring inside the switchgear is simple, and the rest of the wiring is in the collection and control of the inside of the protection cabinet. carry out.

(4) scalability. The system design can consider the user's future needs of substation size and function expansion.

(5) Good compatibility. The system consists of standardized hardware and software, and is equipped with standard serial communication interfaces and local I/O interfaces. Users can flexibly configure according to their own needs. System software can also easily adapt to the rapid development of computer technology.

2. Design principles of substation automation system
(1) The substation automation system as a sub-system of grid dispatch automation shall obey the overall design of grid dispatch automation. The configuration and functions of the substation automation system shall include the arrangement of the equipment to meet the requirements of grid security, high quality, economic operation, and information layered transmission and resource sharing. in principle.

(2) The functional configuration of decentralized systems should adopt the principle of decentralization. Functions that can be completed in the bay layer, such as protection, standby power supply, and voltage control, do not need to be completed through the network and the host computer. 220kV junction stations and substations with voltage levels above 220kV should adopt dual and redundant configurations at the network layer and station level to improve system reliability.

(3) According to the actual situation in China, it is unlikely that the substation will be completely unattended. Even if it is unattended, there is a problem of on-site maintenance, commissioning and emergency handling. Therefore, the design should take into account the coexistence of remote and local control operations. Pattern. Similarly, the protection unit should also have the function of remote, on-site switching, and on-line modification of setting values. It is mainly based on distance and on-site shops, and it should be designed and manufactured to ensure that only one of the control methods is valid at the same time.

(4) The design of the access system for the station automation and unattended station should technically ensure that the hardware interface of the station automation system meets international standards. The supporting software of the system complies with the ISO open system regulations. The definition, format, programming, and address of various types of data, communication protocols, and network protocols of the system are consistent with the corresponding power grid dispatching automation systems to meet the development requirements of the power industry informatization.

(5) The integrated design of protection, measurement and control should be actively and cautiously implemented to ensure the relative independence and reliability of the protection function. The SOE resolution of the distributed system is achieved through the protection unit. Protection, measurement, and control In principle, a voltage transformer (TV) can be used in combination. The amount of charge, total power, etc., can be connected to the measuring current transformer (TA), which can be used for monitoring purposes. .

(6) AC sampling technology should be used in the design of substation automation system to reduce TA, TV load and improve measurement accuracy. At the same time, the optical sign screen and the central signal screen can be cancelled, the control screen is simplified, and the computer undertakes the signal monitoring function, so that any information can be collected once and used repeatedly, and the real-time and reliability of information can be improved, and space can be saved. Reduce screen cabinets, secondary cables and design, installation, and maintenance workload.

(7) At present, most of the connections between the components of the decentralized substation automation system at home and abroad mostly use the serial port communication method (RS232C, RS422, RS485 bus, etc.), and their communication speed and resource sharing are limited. It is recommended to use local area network (LAN) communication methods, especially peer to peer networks, such as bus-type networks (media sharing type), that is, each node on the Internet can communicate directly with other nodes on the network. Example CSC-2000 Lon Works Network, DISA-2, DISA-3 used CANnet (control area network) network.

(8) There is a strong electromagnetic field disturbance in the substation. From the viewpoint of anti-electromagnetic interference, optical fiber communication can be preferentially used in the selection of communication media. This is particularly applicable to decentralized substation automation systems. The LSA678, DISA-2, and DISA-3 types all use optical fiber communication. However, given the relatively high installation and maintenance of optical fibers and the relatively high cost, distribution stations should use cables as the communication medium.

3, the development direction of substation automation

(1) Feeder Automation. The development of substation automation has greatly improved the reliability of power supply, but it is necessary to further reduce the time of power outages, and a large part depends on the development of feeder automation. Feeder automation must install electric switches on the feeder line, configure the feeder terminal equipment FTU, install fault indicators for some branch lines, and use the communication system to provide feeder operation data and status to the system and execute feeders issued by the system. Switch remote control operation command non-linear load. Motors start directly, unbalanced loads, welding equipment and household appliances increase, reducing the voltage quality. Voltage quality has a great influence on modern electronic devices and computer systems. For this reason, it is proposed that the system should perform continuous measurement and quality analysis on the voltage and that the noise exceeds the limit alarm. At the same time, different reactive power compensation methods should be selected according to actual needs.

(2) Integration, intelligence and integration. The substation automation system as a large, complex and highly integrated systemic project contains a large number of equipment and subsystems. There are different degrees of correlation between functions and subsystems, and the technology itself and its technologies are in continuous development. Among them, it is impossible for any manufacturer to do everything. In terms of feeder automation, the comprehensive costs of construction, operation and maintenance have been significantly reduced, creating powerful conditions for improving the reliability of power supply. Fault location and automatic restoration of power transmission can significantly reduce power outage time. Effectively solving this problem must be based on digital relay protection, feeder automation, and DMS systems. For fault location, some foreign countries have proposed the use of three kinds of integrated technologies: fault distance calculation method, line fault indicator method, and fault probability statistics method for different line intervals. These information are combined together to perform fuzzy logic processing.

4 Conclusion

With the continuous development of science and technology, computers have penetrated into every corner of the world. The power system has inevitably entered the era of microcomputer control. Substation automation systems have replaced the traditional secondary system of substations and have become the current trend of power system development.